Mechanisms Underlying Persistent Lentivirus Replication in Follicular T Cells

描述（由申请人提供）：在慢性HIV-1和SIV感染中，病毒复制集中在滤泡CD4+ T细胞中的淋巴样组织中，滤泡CD4+ T细胞比滤泡外CD4+ T细胞更容易被有效感染30至40倍。为什么慢病毒优先被滤泡CD4+ T细胞复制，以及为什么病毒特异性细胞毒性T淋巴细胞（CTL）不能抑制这些细胞中的复制，原因尚不清楚。急性SIV感染时，病毒复制不集中在B细胞滤泡中，提示滤泡中病毒的浓度可能与适应性免疫有关。T滤泡辅助细胞（TFH）是抗原特异性细胞的一个特殊子集，它们迁移到B细胞滤泡中，在那里它们与B细胞和滤泡树突状细胞（FDC）相互作用，促进B细胞成熟和抗体产生。我们假设，在慢性HIV-1和SIV感染中，病毒复制集中在TFH内，这是因为1)TFH对生产性慢病毒感染的内在易感性增加，2)TFH位于FDC上邻近抗体-病毒粒子复合物的生发中心（GC），以及3)滤泡CTL的数量和功能缺陷。这些假设将通过使用人类和恒河猴淋巴组织的一系列体外和体内实验进行验证。在Aim 1中，我们将通过GFP报告病毒的体外实验感染，确定人类和猕猴的TFH是否比其他CD4+ T细胞更容易受到生产性慢病毒感染。在目标2中，我们将通过原位组织分析以及在分类的慢病毒亚群中测量病毒RNA，确定慢性和急性慢病毒感染中体内生产性感染T细胞的分布和表型

DESCRIPTION (provided by applicant): In both chronic HIV-1 and SIV infection, virus replication is concentrated in lymphoid tissues in follicular CD4+ T cells, which are 30 to 40 times more likely to be productively infected than extrafollicular CD4+ T cells. Reasons why lentiviruses are preferentially replicated by follicular CD4+ T cells and why virus-specific cytotoxic T lymphocytes (CTL) cannot suppress replication in these cells are not understood. Virus replication is not concentrated in B cell follicles in acute SIV infection, suggesting that te follicular concentration of virus may be related to adaptive immunity. T follicular helper cells (TFH) are a specialized subset of antigen-specific cells that migrate into B cell follicles where they interact with B cells and follicular dendritic cells (FDC) to promote B cell maturation and antibody production. We hypothesize that virus replication is concentrated within TFH in chronic HIV-1 and SIV infection due to 1) increased intrinsic susceptibility of TFH to productive lentiviru infection, 2) their location in germinal centers (GC) adjacent to antibody-virion complexes on FDC, and 3) numerical and functional deficiencies of follicular CTL. These hypotheses will be tested through a series of experiments both in vitro and in vivo using lymphoid tissues from humans and rhesus macaques. In Aim 1, we will establish whether human and macaque TFH are intrinsically more susceptible to productive lentivirus infection than other CD4+ T cells through in vitro experimental infections with GFP reporter viruses. In aim 2, we will determine the distribution and phenotype of productively infected T cells in vivo in both chronic and acute lentivirus infection by in situ tissue analyses as well as measuring viral RNA in sorted subsets of cells. In Aim 3 we will investigate the hypothesis that numerical and/or functional deficiencies in follicular CTL contribute to the propagation of HIV-1 within B cell follicles using in situ studies in vitro assays of follicular CTL function, and CD8 depletion of rhesus macaques in vivo. In the context of all aims, we will evaluate the impact of T follicular regulatory cells (TFR), on HIV-1 replication and CTL function. Collectively, these studies will provide a wealth of new information on the cells that foster HIV-1 replication in B cell follicles and factors in the follicular milieuthat may promote or impair lentivirus replication. A better understanding of the mechanisms that underlie permissiveness of follicular CD4+ T cells to lentiviruses is vital to development of a protective vaccine or a functional cure for HIV-1.